Reducing Roaming Handoff Time for Improved User Experience in IEEE 802.11 Networks

The document discusses strategies to minimize roaming handoff time in IEEE 802.11 networks, focusing on enhancing user experience for latency-sensitive applications like video conferencing and online meetings. Emphasizing the importance of low latency in areas such as AR/VR and voice-over-Wi-Fi applications, the observations and testing aim to optimize the handoff process for seamless connectivity. Various stages of roaming handoff are analyzed, shedding light on potential delays and improvements required for a smoother transition.

• Roaming Handoff
• IEEE 802.11
• User Experience
• Latency-sensitive Applications
• Connectivity Optimization

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1. November 2022 doc.: IEEE 802.11-22/1874r2 Roaming handoff time reduction to improve user experience Date: 2022-xx-xx Authors: Name Affiliations Address Phone email Xiaokun Hu Lei Zheng Jianxiang Chen Ruijie Networks Inc Ruijie Networks Inc Ruijie Networks Inc huxiaokun@ruijie.com.cn zhengl@ruijie.com.cn chenjianxiang@ruijie.com.cn Lingwu Sun Ruijie Networks Inc sunlingwu@ruijie.com.cn Lihua Zhu Ruijie Networks Inc zhulihua@ruijie.com.cn Submission Slide 1 Xiaokun Hu, Ruijie Networks Inc

2. November 2022 doc.: IEEE 802.11-22/1874r2 Abstract Introduction Observation Some suggestions Conclusion Submission Slide 2 Xiaokun Hu, Ruijie Networks Inc

3. November 2022 doc.: IEEE 802.11-22/1874r2 Introduction With the rise of mobile working, more and more latency-sensitive applications, such as video conferencing and online meeting, are widely used. Although IEEE 802.11k/v/r have greatly reduced the time consumption of BSS detection and authentication during roaming; IEEE 802.11e has reduced the transmission latency of audio and video packets. However, up to now, the actual Wi-Fi roaming handoff process sometimes still makes users feel video and call interruptions. Submission Slide 3 Xiaokun Hu, Ruijie Networks Inc

4. November 2022 doc.: IEEE 802.11-22/1874r2 Introduction The Cloud AR/VR Whitepaper [3] published by GSMA says: The latency requirement for the overall end- to-end in VR is commonly targeted at 20 ms. In AR, the requirement is even stricter. Some sources identify the limit for a perfect AR experience at 5 ms. The Wi-Fi Alliance provides Voice-Enterprise certification[2], aimed at voice over Wi-Fi application. The Latency threshold is below 50 ms. Submission Slide 4 Xiaokun Hu, Ruijie Networks Inc

5. November 2022 doc.: IEEE 802.11-22/1874r2 Observations shielded box1 adjustable attenuator1 AP1 adjustable attenuator2 Smartphone PC1 shielded box2 Switch AP2 PC2 Roaming handoff time test environment The roaming handoff time test is performed in the shield. The service interruption time during roaming is tested by sending data packets at an interval of 10ms. Submission Slide 5 Xiaokun Hu, Ruijie Networks Inc

6. November 2022 doc.: IEEE 802.11-22/1874r2 Observations The right table shows the average roaming data of some mobile terminals.The roaming process could be divided into three stages: pre-roaming,roaming and post-roaming. In the test, we observed that packets loss or latency occurred in either stage during roaming handoff. Roaming is triggered by BTM Req(11v) Generally, the roaming time is 32.5ms, from Auth to 4WAY handshake For 802.11r support terminals, it can be reduced to 10.5ms. However, if these delay added: 1.packets that are cached in advance due to the cross- channel probe of the terminals before roaming. (T0 to T4) 2. The waiting time between the terminals entering power saving and sending Auth.(T4~T5) 3. After completing the reassociation and stating to send packets.(T9 to T12) Average time consumptio n in each stage Unit: ms Time consumin g in stages Unit: ms Time Phasin g Stage Stage description STAs meet roaming threshold or receive bss transition management(BTM)request, and prepare to send probe request. STAs get into PS status, change to different channels and send probe request STAs receive probe response or not, back to working channel , quit PS status and response to BTM T3-T4STAs decide to roam, refresh state machine,prepare to get into PS mode In working channel, STAs get into PS mode In new channel, STAs send Auth request to a new T0-T1 3.5 T1-T2 25 Pre- roamin g T2-T3 5 47 1 T4-T5 12.5 AP T5-T6 T6-T7 T7-T8 The new AP response to theAuth STAs send Reassoc Req AP reponses to the Reasso Rsp 1 5.5 4 22 Roami ng 32.5(10.5) T8-T9 4 way handshake of WPA2/PSK 0 if 802.11r 5 T9-T10 T10- T11 T11- T12 STAs quit PS mode Post- roamin g STAs start to send /answer packets 15 23 In the worst case, even if 802.11r support device, it would cost average 80.5ms (47ms +10.5ms +23ms) STAs complete to send the packets that buffer before roaming 3 Submission Slide 6 Xiaokun Hu, Ruijie Networks Inc

7. November 2022 doc.: IEEE 802.11-22/1874r2 Some suggestions 1. The station empties the cache more aggressively before roaming. 2. The state machine transition of the terminals(laptop, wireless card, smartphones) and APs in the handoff process is time-consuming. 3. Links are quickly recovered after roaming, and the wireless rate adjustment and aggregation process could be accelerated. Submission Slide 7 Xiaokun Hu, Ruijie Networks Inc

8. November 2022 doc.: IEEE 802.11-22/1874r2 Conclusion Low latency is one important KPI for future wireless networks, according to 4K/AR/VR applications requirements. Current handoff time of roaming between two APs does not meet these requirements, the latency of roaming needs to be further reduced. Submission Slide 8 Xiaokun Hu, Ruijie Networks Inc

9. November 2022 doc.: IEEE 802.11-22/1874r2 References 1. 2. 802.11-18/1231r4, EHT Draft Proposed PAR Wi-Fi CERTIFIED Voice-Enterprise: https://www.wi-fi.org/discover-wi-fi/wi-fi- certified-voice-enterprise Cloud AR/VR Whitepaper: https://www.gsma.com/futurenetworks/wiki/cloud-ar-vr- whitepaper/#_ftn9 3. Submission Slide 9 Xiaokun Hu, Ruijie Networks Inc